Help! My Cat Is Constipated: Treating Constipation

Updated July 25, 2021

‘At A Glance (Details Below)’ Emergency Care

How To Treat Constipation In Cats

  1. See the vet as more than 50% of male cats who are thought to be constipated actually have a urinary obstruction.
  2. True constipation often has very few visible symptoms other than poor appetite and weight loss.
  3. Treatment is via dietary fibre, hyperosmotic laxatives, lubricants, diet & grooming.

Now dive deeper.

Later I’ll explain the diagnosis and treatment of constipation in cats. However, the greatest danger is to mistake constipation for urinary obstruction. That’s why I’ll start with Dante’s story.

The Constipated Cat Who Wasn’t

Dante is a middle-aged male cat who has always been healthy. One day, his owner noticed he was quieter than usual and not eating. He spent the day outside, was seen straining as if trying to poo, and when seen later was collapsed and panting.

She was sufficiently concerned to visit the emergency centre instead of waiting until the next morning to see us. Thank God she did.

Once he was assessed by the vet on duty, it was clear that his bladder was abnormally large, hard and painful. Blood was taken showing dangerous elevations in potassium, urea, and creatinine wastes normally excreted by the kidneys. A urinary obstruction was diagnosed and he was immediately admitted to relieve the blockage.

High blood potassium interferes with the function of the heart, and thus many obstructed cats die of cardiac arrest within hours. We can only imagine the excruciating pain they experience.

To continue the story, visit our page on prevention and treatment of urinary blockages in cats. From now on we’ll only discuss faecal problems.

Signs of Constipation in Cats

The signs of true constipation in cats can be:

  • Unproductive straining or pain on defaecation
  • Small, hard faeces sometimes with blood or mucus
  • Defaecation less than every day
  • Weight loss and poor appetite
  • Intermittent vomiting (read other causes of vomiting in cats here)
  • Lethargy

Most owners are unaware of the problem until it becomes severe and difficult to treat. However, there’s another way.

Diagnosis of Constipation

I diagnose most cats with constipation during a routine checkup. Vets can feel the abnormal accumulation of hard faecal pellets in the abdomen. If we suspect that your cat has just been lazy on that day we can always check again later. However, our first impressions are usually correct.

If the cat is large or difficult to palpate your vet will recommend an xray, which gives a quick and definitive answer. Although the cause of constipation is often not found, we observe that it is more common in older cats and certain breeds such as Burmese, Birman and Manx.

Treatment of Constipation in Cats

It’s vital to start treatment as soon as possible. The longer a cat’s colon is stretched, the weaker it gets, and the harder it is to return to normal.

Start with just one (I begin with lactulose) and gradually adjust doses or add other products. The whole time you need to monitor the consistency and frequency of your cat’s droppings.

Each product  shows a starting dose but  these usually need to be adjusted up or down (‘titrated’) to achieve an optimal result. I recommend a soft, formed stool not unlike dog faeces. Some cats will require a combination of treatments.

Diet Change

Mild cases may respond to a simple change from dry biscuits to a wet-only diet. This can also be better for your cat’s health; visit our page on carbohydrate content in cat foods for more information.

More difficult cases respond better to prescription diets that increase dietary fibre, such as Hills r/d and Hills w/d. Again, these are best used in their wet forms.

An increased water intake should also be encouraged to prevent faeces drying due to low water balance. Click here for advice on getting cats to drink more.


Paraffin-containing products can assist, but in my experience rarely work well on their own. There are several products that come in tube form, usually sold as a hairball treatment. For most owners, medical grade liquid paraffin is more effective.

Paraffin is extremely dangerous if given on its own, as cats can’t swallow it easily. This leads to aspiration pneumonia and death (I have seen this happen). Therefore, if using liquid paraffin, it needs to be mixed well into a wet food. Even then, risks are not eliminated.

Starting doses are usually ¼ to ½ a teaspoon twice a day in the food. It is said that regular use can deplete fat-soluble vitamins.

Hyperosmotic Laxatives

These in my experience are the most effective and best tolerated. They work by remaining intact in the colon, where they draw water into the faeces. The amount of water depends on the dose given.

My favourite is lactulose. A common Australian brand, Actilax, is pictured above. It is cheap and readily available at pharmacies. Once again, doses are usually ¼ to ½ a teaspoon twice a day in the food.

I have much less experience using propylene glycol but my reading suggests it is a more hazardous and less effective option.

Bulk Forming Laxatives

Soluble dietary fibre is well-known as an aid to regularity. It also works in cats, but the problem can be getting them to take it. Two such products are pictured above.

I recommend starting Metamucil or other unflavoured psyllium granules at the same doses of ¼ to ½ a teaspoon twice a day in the food. If cats refuse it, I then use Benefiber,  a wheat gluten product which is usually better tolerated. Start Benefiber at much lower doses of 1/16 teaspoon twice a day and increase to effect.

Both are best mixed in the food just before feeding to avoid them turning into gel too early. These products will produce a larger stool with an almost rubbery consistency if over-used.


We shouldn’t forget the effect that ingested hair can have, especially in longer-haired breeds like Ragdoll and Birman. These benefit from frequent brushing to remove dead hair, and in some cases, cats even need full body clipping twice a year.

Treatment of Severe Constipation

Many cats in the beginning, especially if the diagnosis is late, will need an enema performed under anaesthetic.  Sometimes it will need to be repeated intermittently even in well-managed cases. That’s why daily cleaning of the litter tray is almost essential as an early warning.

The late stage of chronic constipation in cats is called megacolon. Everything we’ve suggested so far is an effort to avoid this. While it can still respond to medical management, megacolon often needs to be surgically treated by removal of the colon.

Have something to add? Comments are welcome below and will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These help topics are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story! The information provided here is not intended to be used as a substitute for going to the vet. If your pet is unwell, please seek veterinary attention.


2 Replies to “Help! My Cat Is Constipated: Treating Constipation”

  1. My vet suggested inulin- I have been giving 1/4 tsp twice daily in food with success – I dissolve it in a little water and mix it in meat, no issues of rejection, faeces improved from small hard pellets to more bulky soft stools. Bioglan make it with Jerusalem artichoke available from larger chemists.

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